# Difference between revisions of "Dictionary:Dielectric constant (ε)"

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(dī, ∂ lek’ trik) A measure of the capacity of a material to store charge when an electric field is applied. It is the dimensionless ratio of the capacitivity or permittivity, the ratio of the electrical displacement D to the electric field strength E, of the material to that of free space:

${\displaystyle {\textbf {D}}=\varepsilon {\textbf {E}}}$.

Also called specific inductive capacity. It is frequency and temperature dependent. Typical values are 1.0 for air, 80 for water, 5-20 for granite, 3-100 for dry-to-moist sand. A complex relative permittivity ${\displaystyle \varepsilon ^{\star }}$ is sometimes used:

${\displaystyle \varepsilon ^{\star }=\varepsilon -j\epsilon '}$,

where ${\displaystyle \epsilon '}$ is the dielectric loss factor, a measure of the loss of energy through conductivity, polarization currents, etc.